In Japanese Patent Application No. 5-225269 (Japanese Patent Laid-Open Application No. 7-83424), the present inventors and others proposed a fluidized bed incinerator which resolves problems arising in the rapid combustion of material for incineration introduced into a fluidized bed material consisting of a fluid medium, such as silica or the like, and unburnt waste and combusted ash.
In this fluidized bed incinerator, a pair of partitioning walls extending from the side by the inlet for material for incineration to the side by the ash discharge outlet are provided on either side of the bed surface of a combustion chamber in a furnace main unit, such that the combustion chamber is divided into three in a lateral direction, thereby separating the fluid layer into a central fluid layer and right and left side fluid layers. Emission pipes for fluidizing air are provided respectively in the base section of each fluid layer and are composed such that, by controlling the speed of the dispersive air emitted from the emission pipes in each fluid layer, the fluidized bed material circulates fluidly in succession from the central fluid layer by the inlet towards the central fluid layer by the discharge outlet towards the side fluid layers by the discharge outlet .fwdarw. the side fluid layers by the inlet.
According to the composition described above, stable combustion is achieved, whereby the fluid speed of material for incineration introduced into the central fluid layer by the inlet is reduced, the material combusts slowly, and moreover, the generation of carbon monoxide and dioxin can be suppressed.
However, the following problems have been observed in the an aforementioned composition for a fluidized bed incinerator.
(1) In order to raise thermal resistance and durability, the partitioning walls are water-cooled partitioning walls comprising in-built water pipes, and therefore the thickness of the partitioning walls is increased, the bed surface of the central fluid layer becomes narrower and this bed surface area cannot be used effectively. Furthermore, the structure is complex and equipment costs increase.
(2) If the height of the fluid layers changes, then the relationship between the fluidized bed material and the height of the partitioning walls will change, making it difficult to achieve stable circulation of the fluidized bed material, and therefore requiring control of the layer height and fluid speed.
(3) In order to broaden the bed surface of the central fluid layer by the inlet, in structural terms, the side fluid layers by the inlet have a narrow surface area and the outlet space at the top of the partitioning walls becomes narrow. Therefore, it is necessary to propel the fluidized bed material upwards at a high fluid speed in order that it is transmitted from the side fluid layers by the inlet to the central fluid layer by the inlet, and hence the fluid speed of the fluidized bed material cannot be reduced in this region. Consequently, there is a limit to the extent to which the fluid speed of the fluidized bed material in the central fluid layer can be reduced.
(4) Since the side fluid layers by the inlet and the central fluid layer by the inlet are covered by low, arc-shaped ceiling partitions which guide the fluidized bed material, they do not receive heat radiated from combustion of pyrolyzed gases, or the like. Therefore, thermal efficiency declines and the temperature of the central fluid layer by the inlet and the central fluid layer by the outlet is reduced excessively.